The present invention relates to a coil part obtained by sealing a coil with a conductor wound on a bobbin with a resin, and more particularly to a coil part capable of efficiently guiding out a magnetic flux generated to the outside and moreover efficiently radiating heat generated to the outside. The present invention also relates to a coil part capable of generating a high magnetic flux density even when a low electric current is used. The coil parts according to the present invention can be applied to various kinds of relays, actuators, switches and the like.
A coil is an electric circuit device constructed by winding a conductor on the surface of an insulator and having a self-inductance. When an electric current is passed through the coil, a magnetic flux is generated to accelerate electromagnetic induction and the action of electromagnetic force. There have heretofore been known coil parts sealed with a resin for the purpose of protecting a coil from external environments such as temperature, humidity and shock and conducting electrical insulation. More specifically, there are coil parts obtained by winding a conductor around a bobbin (insulating spool for supporting the resulting coil) made of a synthetic resin to form a coil and sealing the periphery thereof with a synthetic resin.
The coil parts of such a structure are widely used in fields of relays, actuators, switches and the like. A high electric current has had to be passed through the coil for smoothly conducting the operation of such a coil part. However, when a high electric current is passed through the coil, heat may be generated to heat-deform the synthetic resin-made bobbin and the portion sealed with the resin by heat accumulation in some cases.
It has heretofore been attempted to seal the whole coil with a magnetism-permeable resin composition comprising a synthetic resin and powdered magnetic material. However, such a resin composition has involved a problem that it is difficult to efficiently guide out a magnetic flux generated to the outside.
It is an object of the present invention to provide a coil part capable of efficiently guiding out a magnetic flux generated to the outside and moreover efficiently radiating heat generated to the outside.
Another object of the present invention is to provide a coil part capable of smoothly conducting operation even when a low electric current is used.
More specifically, it is an object of the present invention to provide a coil part which is an electronic part obtained by sealing a coil with a conductor wound on a synthetic resin-made bobbin with a synthetic resin, may be operated with a low electric current, scarcely undergoes temperature rise and efficiently guides out a magnetic flux to the outside.
The present inventors have carried out an extensive investigation with a view toward overcoming the above-described problems involved in the prior art. As a result, it has been found that when a coil with a conductor wound on a bobbin is sealed with a high heat-conductive and magnetism-impermeable resin composition, heat generated can be efficiently radiated to the outside, and a magnetic flux generated can be efficiently guided out to the outside. Further, when a bobbin formed by a magnetism-permeable resin composition is used, a high magnetic flux density can be generated even when a low electric current is used. The present invention has been led to completion on the basis of these findings.
According to the present invention, there is thus provided a coil part obtained by sealing at least part of the periphery of a coil with a conductor wound on a bobbin with a high heat-conductive and magnetism-impermeable resin composition (A).
The bobbin may be formed from a synthetic resin composition such as a magnetism-permeable resin composition or magnetism-impermeable resin composition. It is preferred to use a bobbin formed from the magnetism-permeable resin composition in that a high magnetic flux density is generated with a low electric current.
The resin seal means that the whole or a part of the periphery of the coil is wrapped and embedded in the high heat-conductive and magnetism-impermeable resin composition (A). When the coil with the conductor wound on the bobbin is sealed with the resin, there can be provided a coil part which is protected from environments such as humidity, active gasses, vibration and shock and improved in heat-radiating ability.